The Value of Myocardial Perfusion Imaging for Diagnosing Coronary Artery Disease in Patients with Aortic Valve Stenosis

Angina is a common symptom in patients with AS with or without accompanying CAD. When due to the valvular obstruction alone, the pathophysiology involves mismatch between reduced diastolic coronary flow and increased LV mass, or impaired coronary vasodilator reserve. When CAD is present, the severity of angina correlates with the extent of CAD, which tends to be inversely related to the degree of valvular obstruction at presentation. It is important to make a correct diagnosis of CAD in AS patients pre-operatively, since this factor significantly influences peri-operative morbidity and long-term survival. Whether MPI in AS patients can completely exclude CAD and eliminate the need for coronary angiography is a difficult question. Approximately 350 AS patients having had MPI have been reported. The studies differ in terms of scintigraphic technique (planar versus SPECT), stress modality, isotopes used, and definitions of an abnormal scan and what constitutes hemodynamically significant coronary stenosis. The 'best case' diagnostic data showed sensitivity of 87%, specificity 72%, positive predictive value of 81%, and negative predictive value of 86%. These figures indicate a high degree of accuracy and are comparable to the results of MPI in patients without AS. However, the data suggest that the diagnosis of coronary disease is missed by MPI in 14% of AS patients with CAD. Review of the referenced series indicates that in many cases, the stenoses were hemodynamically significant, and were important to identify pre-operatively to avoid operative morbidity and improve long-term prognosis. Thus, in conclusion, although MPI is highly accurate in AS patients, a normal study cannot totally exclude the diagnosis of CAD. Coronary angiography should continue to be performed, particularly in patients with angina, or who are at risk for CAD because of their risk factor profile.